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In the present study, detailed comparative experiments on a heavy-duty diesel engine used in the world harmonized transient cycle (WHTC) and road spectrum reversely deduced cycle (RSRDC, which was derived from a road test) were carried out. Fuel consumption and gaseous and particulate pollutants, along with some engine operation parameters, were measured transiently; thus, specific emissions can be calculated. Results showed that the BSFC of WHTC and RSRDC was 201.8 and 210 g/kW·h, respectively, because the real road driving cycle (RSRDC) had wider operating point distributions and more points located in the low-efficiency zone relative to WHTC. Thus, WHTC operations exhibited higher raw CO (abundant CO formation needed a specific temperature threshold) and NOx but lower HC. Furthermore, with aftertreatment, all pollutants met the newest China regulation limit. Finally, transient emissions were analyzed in detail. Although the specific emissions of some pollutants were similar in value for both cycles, transient processes may largely be different. Therefore, the current study is meaningful, and we not only provide broad and detailed information but also directly compare two types of operations (one is a real road driving cycle) in the laboratory: this is rarely discussed in the literature. [ABSTRACT FROM AUTHOR]

Non-road emission regulations are becoming increasingly rigorous, which makes it necessary for non-road engines to adopt aftertreatment systems. The commonly used aftertreatments mainly include diesel oxidation catalytic (DOC), diesel particulate filter (DPF), particle oxidation catalyst (POC), selective catalytic reduction (SCR) and ammonia purification catalyst (ASC). The purpose of this study is to investigate the effects of using an integrated system (DOC + DPF/POC + SCR + ASC) on non-road diesel engine emissions under steady-state and transient operating conditions, respectively. The major works are the comparison between POC and DPF from the viewpoint of emission reduction. The results show that both POC and DPF can effectively reduce particulate matter (PM) and nitrogen oxide (NO X) emissions under steady-state conditions, and DPF has better purification effect than POC, especially for PM. The PM conversion rate of DPF is up to 87%, while that of POC is only 60% under the non-road steady-state test cycle (NRSC). Both NO X and hydrocarbon (HC) conversion rates are high, exceeding 95%. The conversions of PM, NO X , HC, and carbon monoxide (CO) of DPF in the non-road transient test cycle (NRTC) are 92.83%, 96.99%, 96.86% and 81.45%, respectively, while those of POC are 60.12%, 95.45%, 92.82% and 79.51%, respectively. Both the POC and DPF systems can meet the emission regulation limits. As a result, POC has the potential to substitute DPF in non-road engines due to its lower product and maintenance costs. We hope that the comparison study will provide useful guidance for improving the emissions performance of non-road diesel engines. • Alternate outlet plugging POC and both inlet and outlet alternate plugging DPF were used. • Comparative study of POC and DPF aftertreatment systems was performed at various working conditions. • Transient exhaust state and emissions are analyzed in detail. • POC has the potential to replace DPF under current emission regulation. [ABSTRACT FROM AUTHOR]

For investigating the temperature distribution of cylinder head under the coaction of burned gas and coolant, the temperature field of the cylinder head of a diesel engine is analyzed with fluid-solid coupling technique. Firstly, a CFD analysis is carried out on in-cylinder working process and water jacket with software AVL-Fire, and the thermal boundary conditions for the wall surfaces of cylinder and water jacket are obtained. Then the thermal boundary conditions are mapped to FE meshes, and the temperature field of cylinder head is calculated by FE analysis. The results demonstrate that the highest temperature of cylinder head is far lower than the permissive temperature of material, and the temperature distribution rationally explains the "heat" working environment of cylinder head. [ABSTRACT FROM AUTHOR]

• Energy balance and emissions of a non-road diesel engine were measured under Non-road Transient Cycle. • A new concept "thermal delay effect" is proposed to explain the cooling loss. • PN decreases to 4.30E + 09 #/kW·h by diesel particulate filter with efficiency of 99.99%. • CO and HC are reduced to zero and NOx by 24.3% with diesel oxidation catalyst. • Engine load plays the dominant role on non-road diesel engine emissions. In the current study, the interaction between energy flow and aftertreatment is investigated by experiment to explore the energy distribution pattern changed by aftertreatment and the reversed impact on emission reduction. The temperature distribution, THC, CO/CO 2 , NOx and PN (particle number) emissions were measured in a non-road diesel engine with and without aftertreatment, DOC (diesel oxidation catalyst) and DPF (diesel particulate filter), under NRTC (non-road transient cycle) driving. With aftertreatment, the cooling loss is the main source for thermal efficiency reduction, a new concept "thermal delay effect" is proposed to explain this phenomenon. For emissions, overall CO and HC are almost reduced to zero through DOC, although CH 4 conversion efficiency is only about 30%; NOx conversion efficiency is ~ 24.3%; and PN filtration efficiency is 99.99% through DPF. The engine meets the China national emission regulation even without aftertreatment except for PN, but PN decreases by five orders of magnitude through DPF. Finally, the emissions histories were analyzed in detail. The influencing factors were discussed thoroughly for original scenario. The exhaust temperature coupling with properties of catalytic converter were employed to analyze the aftertreatment's performance and its impact patterns on pollutants. Under operation pattern of back pressure compensation, the average exhaust temperature (300 °C) under aftertreatment scenario increased by 6% relative to without aftertreatment, while during most time it did not exceed 350 °C at which the NOx conversion began to drop. Thus this operation made a good trade-off among reductions of various pollutants. Therefore, the energy distribution analysis must be from the view point of integration between engine body and whole exhaust system to be sure of clarification about aftertreatment's behaviors. [ABSTRACT FROM AUTHOR]

• The throttling effects on performances of a heavy-duty diesel engine were explored. • The throttle response of this engine is more sensitive than those in literature. • Exhaust temperature is largely improved after 60 % throttling degree. • Air flow and thermal status were optimized at real driving without much payments. • NOx decreases by ∼43 % after optimizations while fuel consumption is kept unchanged. Heavy duty diesel engines emit over half of mobile source NOx, so SCR is used to reduce NOx. But in applications, SCR is hard to work in desired temperature range. In this work, we try to improve exhaust thermal management and finally reduce NOx through intake throttling effect. Firstly a throttle was designed and its response characteristics were widely explored through steady-state experiment. Results showed that exhaust temperature can be raised largely through intake throttling degree (TD) control, it has obvious effect only after 60 % TD. At 1100 r/min and 65 % TD, exhaust temperature rises by 123.3 °C, 74.2 °C, 49.7 °C and 33.5 °C for 600 N·m, 400 N·m, 200 N·m, and 50 N·m loads, respectively. TD demand for rising transition point becomes larger as engine load decreases, at 600 N·m transition point occurs at 61 % TD, but it increases to 68 % TD at 50 N·m. Finally the intake flow rate was optimized continuously with whole cycle level consideration in transient operation. NOx decreased by 43 % with fuel consumption and HC keeping unchanged, while CO increased by 24.6 %. We hope to provide a good example for diesel engine performance improvement from optimization of existing technologies without too much cost. [ABSTRACT FROM AUTHOR]

[Display omitted] • The purification efficiency characteristics and interactions of each catalyst in the integrated aftertreatment system are revealed. • CO and HC basically achieve almost 0 when the DOC temperature is higher than 600 K. • The NO reaction rate is closely related to DOC temperature. • Inlet pressure of DOC has almost no effect on the conversion of HC and CO. • When the temperature is higher than 500 K, the NOx conversion efficiency of SCR is very high. In this paper, the emission characteristics and catalytic reactors interactions of a non-road diesel engine are investigated under non-road transient cycle (NRTC) by experiment and system level simulation. The results showed that the overall emission conversion efficiency of hydrocarbon (HC), carbon monoxide (CO), nitrogen oxides (NO X) and particulate matter (PM) is 96.68 %, 91.45 %, 97.67 % and 93.33 %, respectively under NRTC in experiment. In addition, the interactions of each catalytic converter for emissions under NRTC have been obtained through simulation. When the diesel oxidation catalytic (DOC) temperature is higher than 600 K, CO and HC emissions basically achieve almost 0 through DOC purification. Furthermore, DOC can convert nitric oxide (NO) into nitrogen dioxide (NO 2) which provides strong oxidation for the passive regeneration of diesel particulate filter (DPF). The NO reaction rate is closely related to DOC temperature. And the average conversion efficiency from NO to NO 2 in DOC is 40.36 %. Moreover, the DOC inlet pressure has almost no effect on the conversion of HC and CO. When the temperature of selective catalytic reduction (SCR) is higher than 500 K, the averages NOx conversion efficiency of SCR is up to 98.74 %. And ammonia purification catalyst (ASC) can further reduce NO emissions while absorbing slip ammonia. When the inlet temperature of DPF is more than 520 K, it has almost no effect on the oxidation of PM. The PM conversion efficiency of aftertreatment system (ATS) is mainly affected by the PM collection efficiency of DPF. The average PM collection efficiency of DPF is 53.32 %, while the PM conversion efficiency of ATS is 91.54 % by simulation. Although DPF will convert PM to CO, these CO cannot be completely converted into carbon dioxide (CO 2). So the CO conversion efficiency of ATS is lower than that of DOC. [ABSTRACT FROM AUTHOR]

In this study, the bench test of a non-road diesel engine was conducted under universal conditions, non-road steady-state cycle (NRSC) and non-road transient cycle (NRTC). To reduce the raw emissions of the tested non-road diesel engine, some improvement measures, such as pre-injection, smoke limit, and intake throttle degree control strategy, were applied to the optimized engine. The experiment results showed that particulate matter (PM) emissions are reduced significantly at medium-high speed and low load. The maximum and average proportion of PM emissions reduction at 0–30% load and 1400–2200 r/min are 68.4% and 47.5%, respectively. However, the optimized nitrogen oxide (NOx) emissions are higher than that of the original engine, particularly under low load working conditions. Nevertheless, at medium-high speed and load, NOx emissions of the optimized engine were reduced. PM and NOx emissions decreased by 12.3% and 2.4%, respectively, under NRSC. Under NRTC, PM and NOx emissions decreased by 5.2% and 5.5%, respectively. Unburned hydrocarbon (HC) and carbon monoxide (CO) were always maintained at extremely low emission levels. Furthermore, the fuel consumption almost remained constant under all operating conditions. Thus, this study demonstrates the emission reduction potential in non-road diesel engines without considerable payment. • Universal characteristics, NRSC and NRTC tests were conducted. • Pre-injection, smoke limit and intake throttle opening strategies were proposed. • PM and NOx emissions decreased by 12.3% and 2.4%, respectively under NRSC. • PM and NOx emissions decreased by 5.2% and 5.5%, respectively under NRTC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Three POC modes were tested under NRTC and compared to original emissions. • The impact of POC structure on back pressure and exhaust temperature was investigated. • Asymmetric layout and plugging structure has the best purification effect on NOx and PM. • Exhaust temperature and residence time are key factors for emission reduction under same catalyst. Non-road diesel engine emissions present a serious hazard to both users and the environment. Despite several research on the emission control of non-road diesel engines, the role of particle oxidation catalysts (POC) in emission reduction is still not fully understood. Therefore, the current study investigates this factor during transient operation. The emissions of three modes, POC1 (symmetric layout and plugging channel), POC2 (asymmetric layout and unplugging channel), and POC3 (asymmetric layout and plugging channel), were tested and compared to the original emissions. The experimental results show that the conversion efficiencies of the POC1–POC3 systems for particulate matter (PM) were 33 %, 53 %, and 61 %, respectively. The asymmetrical channel layout can increase the PM conversion efficiency by 28 % compared with the symmetrical channel layout, and the plugging structure can increase the PM conversion efficiency by 8 %. The conversion efficiency of nitrogen oxides (NOx) is above 87 %, and the asymmetric channel layout can increase it by 8 %. However, the plugging structure has almost no effect on the conversion of NOx when compared to the results for POC2 and POC3. HC and CO emissions were very low in all cases. Overall, only POC3 met the CHINA IV emission standards for non-road diesel engines, and the detailed process is discussed in this paper. The current study can help with after-treatment layout for non-road diesel engines. [ABSTRACT FROM AUTHOR]