DAF Trucks (Netherlands)

Gasoline compression ignition (GCI) has shown the potential to produce diesel equivalent efficiency while achieving ultra-low oxides of nitrogen (NOx) and soot emissions. Nonetheless, mechanical constraints under high load conditions have limited its implementation. A partially premixed compression ignition (PPCI) - diffusion combustion strategy has been developed to satisfactorily enable high efficiency and clean high-load GCI operation. By utilizing the PPCI-diffusion combustion strategy, this investigation assessed GCI performance experimentally on a heavy-duty diesel engine. Fuel injection strategy (start of injection, split ratio, and injection pressure) and air-handling system boundary conditions were systematically studied as key parameters under medium-to-full load engine operation. Across different engine operating points, GCI optimized using a one-factor-at-a-time approach demonstrated diesel-like fuel efficiency and emissions compared to the diesel baseline over an engine-out NOx range of 2–7 g/kWh. A design of experiments (DoE) based injection strategy optimization was also conducted at the highest fuel efficiency point, targeting 2.8 g/kWh engine-out NOx. The sensitivity of GCI performance to the fuel injection strategy was thoroughly characterized. The optimized fuel injection strategy showed equivalent diesel efficiency with an enhanced NOx-smoke trade-off without exceeding the mechanical constraints on maximum pressure rise rate (MPPR) and peak cylinder pressure (PCP).

The type approval of heavy-duty engines requires measurement of particulates downstream of a proportional to the exhaust flow partial flow dilution system. However, for particle number systems, which measure in real time, this is not necessary and a fixed dilution could be used. In order to assess this dilution possibility, an inter-laboratory exercise was conducted, where a “Golden” system measuring directly from the tailpipe with “hot” (150 °C) fixed dilution was compared with the laboratory regulated systems. Additional “Golden” counters were measuring from 10 nm, below the current cut-off size of 23 nm defined in the regulation, in order to collect data below 23 nm and to confirm that the direct sampling is also possible for smaller sizes. Seven diesel engines and two CNG (compressed naturals gas) engines were used in six laboratories. The results of the “Golden” instruments were within 25% in most cases, reaching 40% in two laboratories for both >23 nm and >10 nm. The repeatability of the measurements (10% to 40%) remained the same for both systems with both cut-off sizes. One test with regeneration showed clear difference between the 10 nm systems, indicating that the thermal pre-treatment only with evaporation tube might not be adequate. Another system measuring from the tailpipe with a fixed “cold” (at ambient temperature) dilution gave differences of up to 50% in most cases (on average +26%). Dedicated tests with this system showed that the differences were the same with fixed or proportional dilution, indicating that it is not the concept that resulted in the overestimation, but the calibration of the system. The main conclusion of this study is that direct sampling with fixed dilution from the tailpipe can be introduced in the future regulation.

In cam–roller follower units two lubricated contacts may be distinguished, namely the cam–roller contact and roller–pin contact. The former is a nonconformal contact while the latter is conformal contact. In an earlier work a detailed transient finite line contact elastohydrodynamic lubrication model for the cam–roller contact was developed. In this work a detailed transient elastohydrodynamic lubrication model for the roller–pin contact is developed and coupled to the earlier developed cam–roller contact elastohydrodynamic lubrication model via a roller friction model. For the transient analysis a heavily loaded cam–roller follower unit is analyzed. It is shown that likewise the cam–roller contact, the roller–pin contact also inhibits typical finite line contact elastohydrodynamic lubrication characteristics at high loads. The importance of including elastic deformation for analyzing lubrication conditions in the roller–pin contact is highlighted here, as it significantly enhances the film thickness and friction coefficient. Other main findings are that for heavily loaded cam–roller follower units, as studied in this work, transient effects and roller slippage are negligible, and the roller–pin contact is associated with the highest power losses. Finally, due to the nontypical elastohydrodynamic lubrication characteristics of both cam–roller and roller–pin contact numerical analysis becomes inevitable for the evaluation of the film thicknesses, power losses, and maximum pressures.

<div class="section abstract"><div class="htmlview paragraph">This paper presents the identification and validation of a dynamic Waste Heat Recovery (WHR) system model. Driven by upcoming CO₂ emission targets and increasing fuel costs, engine exhaust gas heat utilization has recently attracted much attention to improve fuel efficiency, especially for heavy-duty automotive applications.</div><div class="htmlview paragraph">In this study, we focus on a Euro-VI heavy-duty diesel engine, which is equipped with a Waste Heat Recovery system based on an Organic Rankine Cycle. The applied model, which combines first principle modeling with stationary component models, covers the two-phase flow behavior and the effect of control inputs. Furthermore, it describes the interaction with the engine on both gas and drivetrain side.</div><div class="htmlview paragraph">Using engine dynamometer measurements, an optimal fit of unknown model parameters is determined for stationary operating points. From model validation, it is concluded that the identified model shows good accuracy in steady-state and can reasonably capture the most important dynamics over a wide range of operating conditions. The resulting real-time model is suitable for model-based control.</div></div>

This chapter deals with numerical solutions for the powersplit problem for hybrid vehicles using predefined power and velocity trajectories. Two numerical solution methods are pursued: an indirect method that uses the necessary conditions for optimality obtained with Pontryagin’s Minimum Principle, and a direct method using the Dynamic Programming algorithm which is based on Bellman’s Principle of Optimality. Both methods are illustrated with an example.

This Introduction presents a motivation for the use of hybrid vehicles and provides a general introduction to control in hybrid vehicles. The main motives for implementing hybrid technologies are an improvement in fuel economy and a reduction of exhaust gas emissions. The main hindrances are the added component complexity, the restrictions on the operational regime (optimality in the presence of constraints), and the associated cost. Some alternatives that achieve the same benefits, but which may add other impediments, also deserve mentioning. A road map for hybrid technology, based on past, current and expected trends, outlines what could be done with this technology. This starts with remarks about general aspects and culminates in a discussion about the possibilities of control.