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The conventional diesel engine retarder is an add-on system that converts the power producing diesel engine into a power absorber by altering engine valve timing when vehicle retarding is desired. The retarding effect is achieved by releasing the compressed air charge near TDC compression to prevent energy from returning to the engine during expansion. Retarding performance is optimized only at one engine speed and the increased height due to the add-on approach is a disadvantage for some vehicle applications. This study introduces an integrated Variable Valve Timing (VVT) engine retarder (Figure 1) by applying the lost motion principle. The integrated retarding system has significant dimensional advantage over the conventional add-on engine retarder. The lost motion VVT retarder also provides optimized retarding performance over the entire engine operating range.

An alternative to the current drum brakes, with the increased requirements of todays daily service are disc brakes, in that they offer, in contrast to the drum brakes, the following technical advantages and in turn enhance the active safety of modern commercial vehicles when braking: Enhanced brake pedal-feedback and actuation Improved efficiency Little performance losses when high thermal loads occur (fading). In order to be able to determine the improvement potential of disc brakes they will be compared to the commonly employed Simplex drum brakes. Both wheel brake systems (disc-/drum brakes and all variations) were tested on a computer controlled brake dynamometer and in field tests using a heavy duty commercial vehicle (class 8). The results are compared and conclusions drawn regarding “advantages/disadvantages”.

Internal exhaust gas recirculation (IEGR) with retarded injection timing can provide a 30% reduction in diesel nitrous oxide (NOx) emissions and is an attractive solution to meeting NOx emission levels in the range of 3.4-4.0 g/bkW-hr (2.5-3.0 g/bhp-hr) for heavy-duty diesel engines, especially for off-road and vocational applications. At lower NOx emissions levels, IEGR may be used to supplement cooled EGR or to control HCCI combustion. Alternative valve actuation strategies for IEGR are reviewed. A valve actuation system to provide on-off control of IEGR combined with compression-release braking is presented. System design and simulation results are reviewed. Engine performance predictions and initial test data are discussed, including turbocharger sizing and particulate emission considerations. System reliability is calculated using Weibull data from similar proven components.

Simulation tools are essential for the development of advanced engine braking and variable valve actuation systems. GT-Power with a valve lift user model, which includes effects such as valve-train compliance, is used to predict engine performance, valve lift, and cylinder pressure. MATLAB/Simulink with a hydraulic/valve-train dynamic library is used to evaluate factors relevant to system design such as hydraulic circuit pressures, cam follow, valve-seating velocity, and parasitic loss. CFD is used in hydraulic component design and to provide flow resistance data for the system simulation. FEA is used together with the system simulation to evaluate the design durability, including prediction of impact loads. These tools have been applied to the development of a wide range of compression-release braking and variable valve actuation systems, including recent lost-motion and common-rail designs.

Different compression release two-stroke braking concepts are presented and one is thoroughly studied by simulation and test. The two-stroke braking concept studied here is achieved by eliminating the normal exhaust event and opening an exhaust valve near both compression TDC (first braking event) and exhaust TDC (second braking event). A second “intake” is achieved by keeping the exhaust valve open during the normal expansion stroke after the first braking event, allowing exhaust gases to be reintroduced to the cylinder for the second braking event. Excellent correlations are obtained between simulation results and test data. More than a 40% braking power increase has been achieved by using two-stroke braking compared with the conventional single event braking four-stroke cycle.

Virtually all production engines today have some level of electronic control. As features have been added over the years, some of these Electronic Control Units (ECU's) have grown significantly in complexity, size and cost. As Variable Valve Actuation (VVA) systems evolve from simple, mechanically operated systems such as cam phasers to full VVA systems, electronic systems will also need to evolve to control them. This evolutionary path forces many system-level questions to be considered. Some global questions that will need to be considered as the industry continue on this path, are: “What is the optimal level of electronics integration?” “At what point should a distributed engine control system be considered?” There are several key points that need to be considered to properly make these decisions, many of which will be addressed in this paper. A process for how these decisions might be made for a given system will be discussed.

Given the legal requirements for quality assurance of passenger car exhaust emissions worldwide we define our quality assurance system and present the emission laboratories of the Mercedes-Benz assembly plants Sindelfingen and Bremen. We developed a hierarchically structured, multi-level computer system, which enables us to automize emission test procedures, calibration, maintenance of measurement systems and documentation of exhaust data. Test cell computers coordinate the different components of the test cells and perform maintenance and calibration of measurement devices, thus guaranteeing a high measurement quality with reasonable economy. The coordinating level computer, the emission host system (EHS), processes test parameters, controls and supervises the test sequences and evaluates the test results on a statistical basis.

Variable Valve Actuation has been researched and applied to improve engine fuel economy and emissions. The effect on compression release engine retarding has not been considered. Heavy duty diesel engines are recognized for their ability to function as effective vehicle retarders. Many approaches have been taken to convert the power producing diesel engine into a power absorber by altering air flow management. Compression release diesel engine retarding is generated by altering engine valve timing when braking is desired. By releasing the compressed air charge at near TDC compression, the energy absorbed is prevented from returning to the engine during expansion. The net energy loss provides the braking effect. This study discusses the parameters used in system design to achieve maximum performance by using variable valve actuation, VVA, to produce the brake event. Retarding power potential is evaluated by cycle analysis for each system and supported by engine test data.

The purpose of this research was to present and analyze a previously unreported mechanism of injury within the automotive crash environment - spinal burst or compression fractures due to a vertical force component. Spinal burst fractures are comminuted fractures of the vertebral body which are often associated with retropulsed bone fragments into the spinal. Compression fractures are less traumatic fractures of the vertebral body with minimal comminution. Both fracture types can have varying degrees of neurologic deficit. The mechanism of injury is hypothesized to be a high energy compressive load along the axis of the spine initiated through the buttocks and pelvis or through torso augmentation (inertial loading of the lumbar spine by the torso). Four crashes are presented as evidence of this injury mechanism within the automotive crash environment: two in the United States and two in Germany.