Particulate emissions from homogeneous charge compression ignition (HCCI) engines have been usually considered negligible, and the measurement of particulates (PM) with HCCI combustion systems has been extremely rare. A report from Ford and the authors' own recently published work suggest that PM emissions from gasoline HCCI engines should not be neglected. It has been shown that PM emissions for SI and HCCI engines can be very similar, especially in the accumulation mode. In the present work, the influence of inlet air temperature was investigated. A purpose-built inlet air thermal management system was in use for this purpose. An electric heater in line with an air/engine coolant heat exchanger was used to heat inlet air to 30–40°C above standard operation conditions. A water-cooled intercooler was in use during the second set of tests. Inlet air was cooled approximately 20°C below the case where no heating or cooling was implemented. It has been found that increasing the air temperature will lead to a higher concentration of nucleation mode particles (having diameters 10–20 nm) and lower concentration of accumulation mode particles (with diameters 80–90 nm). When inlet air was cooled, a reverse trend has been observed, especially in the accumulation mode. It was also observed that increasing the load will reduce the differences caused by changes in the inlet air temperature. Finally, trends similar to those observed for direct injection spark ignition (DISI) engines have been observed as well. Increasing either engine speed or engine load leads to increased PM emissions.

This work presents a mass and enthalpy balance model for the air intake system of a multi-cylinder Homogenous Charge Compression Ignition (HCCI) gasoline engine. To achieve controlled auto-ignition across a wide range of engine conditions, a system for management of flow and temperature is installed at the air intake to enable the necessary regulation of temperatures and pressures at the inlet ports. In order to facilitate this control, a complete simulation model of the thermal system for a pressure-boosted multi-cylinder HCCI engine has been developed. The system includes a heat exchanger to heat the charge air, a supercharger to boost the charge air pressure, supercharger bypass and finally an intercooler, so that a wide range of combinations of pressures and temperatures can be achieved at the intake ports.The paper discusses the issues associated with control of the properties of charge air needed to extend the envelope of HCCI operation. This extension is one of the main objectives of the CHASE (Controlled Homogeneous Autoignition Supercharged Engine) project. General principles of the model are outlined and some non-standard submodels for the individual components are presented in detail. Model calibration and validation are presented compared with measured data, experimental results for extensions of HCCI regime possible with the use of thermal management as predicted by the model is demonstrated and lastly the guidelines for control of the system are elaborated.

Linear Fresnel Reflectors (LFR) are a type of concentrated solar collector that uses direct solar radiation (DSR) to provide useful heat for a range of applications, including power generation, heating and cooling. This study introduces a simplified analytical method for predicting the optical and thermal performance of LFR systems using only the geometric parameters and meteorological data of a location. In this analysis, the Incident Angle Modifier (IAM) and DSR are calculated using long-term data from open-access weather datasets, offering analysis from minute-scale to annual resolution, without the requirement of computationally expensive methods such as ray-tracing or extensive onsite measurements. The model is validated against experimental data from an installed LFR system at the Cyprus Institute (CyI) in Nicosia, Cyprus, demonstrating good agreement in both solar and useful energy output. The latter is derived as the product of the predicted DSR, which closely matches pyrheliometer measurements over a four-year period, and the accurately reproduced IAM. Overall, the method provides a reliable estimation of the thermal performance, offering a practical tool for early-stage design for any location of interest, yielding results significantly faster and at a fraction of the computational cost compared to ray-tracing and CFD approaches.