• Energy Research
• 2016-2025close

Several studies have aimed to convert diesel engines to dual- or tri-fuel engines to improve their fuel economy and reduce the emissions from diesel engine, however, most of these studies do not consider enhancing the homogeneity of fuel mixtures inside the engine and accurately controlling the air fuel ratio. In this study, a new air-fuel mixer was designed, manufactured and tested. The proposed air-gaseous fuel mixer design was conceived to be suitable for mixing air with compressed natural gas (CNG) and a blend of hydrogen and compressed natural gas (HCNG) that gives homogenous mixtures with high uniformity index and also to be easily connected with an Electronic Control Unit (ECU) for controlling accurately the air-gaseous fuel ratio for different engine speeds. For optimizing the homogeneity inside the new mixer, fourteen different mixer models were created to investigate the effects of diameter, location, and the number of holes inside the mixer on the homogeneity and distribution of the mixtures. Computational fluid dynamics analysis software was used to check the flow behavior, distribution and homogeneity of mixtures inside the new mixer models. The simulation results revealed that the best uniformity index (UI) values are obtained in model 7 where the UI values are 0.939 and 0.937, respectively, for an air fuel ratio for a blend of hydrogen and compressed natural gas (AFRHCNG) = 51.31 and the air fuel ratio for compressed natural gas (AFRCNG) = 34.15. According to the numerical and experimental results for the new mixer (model 7) under different engine speeds (1000–4000) and air-CNG ratio of 34.15, a meaningful agreement is reached between the experimental and numerical values for AFRCNG (coefficient of determination (R2) = 0.96 and coefficient of variation (CoV) = 0.001494).

Several studies have aimed to convert diesel engines to dual- or tri-fuel engines to improve their fuel economy and reduce the emissions from diesel engine, however, most of these studies do not consider enhancing the homogeneity of fuel mixtures inside the engine and accurately controlling the air fuel ratio. In this study, a new air-fuel mixer was designed, manufactured and tested. The proposed air-gaseous fuel mixer design was conceived to be suitable for mixing air with compressed natural gas (CNG) and a blend of hydrogen and compressed natural gas (HCNG) that gives homogenous mixtures with high uniformity index and also to be easily connected with an Electronic Control Unit (ECU) for controlling accurately the air-gaseous fuel ratio for different engine speeds. For optimizing the homogeneity inside the new mixer, fourteen different mixer models were created to investigate the effects of diameter, location, and the number of holes inside the mixer on the homogeneity and distribution of the mixtures. Computational fluid dynamics analysis software was used to check the flow behavior, distribution and homogeneity of mixtures inside the new mixer models. The simulation results revealed that the best uniformity index (UI) values are obtained in model 7 where the UI values are 0.939 and 0.937, respectively, for an air fuel ratio for a blend of hydrogen and compressed natural gas (AFRHCNG) = 51.31 and the air fuel ratio for compressed natural gas (AFRCNG) = 34.15. According to the numerical and experimental results for the new mixer (model 7) under different engine speeds (1000–4000) and air-CNG ratio of 34.15, a meaningful agreement is reached between the experimental and numerical values for AFRCNG (coefficient of determination (R2) = 0.96 and coefficient of variation (CoV) = 0.001494).

In diesel—compressed natural gas (CNG) dual fuel systems, the CNG is generally inducted into the intake manifold by a CNG mixer mounted at the intake manifold, while the diesel fuel is directly injected into the engine cylinder using a diesel fuel injector system. The poor mixing performance of gaseous mixers is among the causes of unsatisfactory engine performance and lethal exhaust emissions. Based on an existing mixer model, four different models of mixers with 29 cases were created in this study to investigate the effects of the diameter, location, and number of holes inside the existing mixer on the homogeneity and distribution of the mixture. A computational fluid dynamics analysis software was used to check the flow behavior of the CNG and air inside the existing and new mixer models, with the new model being fixed on a 3.2 L engine. These models were examined depending on the maximum speed of the engine (4000 rpm), the full-opened valve, and the stoichiometric air–fuel ratio (34.6). Compared with the new mixer models, the existing mixer model shows a non-uniform methane and air distribution. Model 4/case 26 shows a uniform distribution of the CNG-air mixture with the best homogeneity. This model was then examined to check the flow characteristics of CNG and air at different engine speeds (1000, 2000, 3000, and 4000 rpm). Model 4/case 26 also shows a stoichiometric air–fuel ratio depending on the engine speed.

In diesel—compressed natural gas (CNG) dual fuel systems, the CNG is generally inducted into the intake manifold by a CNG mixer mounted at the intake manifold, while the diesel fuel is directly injected into the engine cylinder using a diesel fuel injector system. The poor mixing performance of gaseous mixers is among the causes of unsatisfactory engine performance and lethal exhaust emissions. Based on an existing mixer model, four different models of mixers with 29 cases were created in this study to investigate the effects of the diameter, location, and number of holes inside the existing mixer on the homogeneity and distribution of the mixture. A computational fluid dynamics analysis software was used to check the flow behavior of the CNG and air inside the existing and new mixer models, with the new model being fixed on a 3.2 L engine. These models were examined depending on the maximum speed of the engine (4000 rpm), the full-opened valve, and the stoichiometric air–fuel ratio (34.6). Compared with the new mixer models, the existing mixer model shows a non-uniform methane and air distribution. Model 4/case 26 shows a uniform distribution of the CNG-air mixture with the best homogeneity. This model was then examined to check the flow characteristics of CNG and air at different engine speeds (1000, 2000, 3000, and 4000 rpm). Model 4/case 26 also shows a stoichiometric air–fuel ratio depending on the engine speed.

The aim of the current study is to evaluate the performance of a domestic water heating system for residential areas in Baghdad climatic conditions for substituting electric water heaters with solar-powered water heaters using solar collectors. Many countries, such as Iraq, are sluggish with electric power issues while receiving very high solar insolation. Solar energy is a clean, non-depleting and low-cost source that can be used especially in residential areas, which forms a great percentage of energy consumption by replacing electric water heating with solar water heating to reduce electricity usage. Therefore, six flat plate solar collectors with an absorbing area of 1.92×0.85 m with one 4 mm thick glass cover are utilized for experimental investigation under the Baghdad climatic conditions. The collector was tested under steady-state settings, which assumed that sunlight intensity, ambient temperature, and inlet-outdoor temperature difference in each collector in the system were constant throughout the operation. According to the experimental results, during the test months of November, December, January, and February, the time-weighted experimental daily average collector array efficiency is found in the range of 40 % to 60 %. Furthermore, the greater energy gain and performance of the solar collector array attain a peak value at solar noon. Additionally, a solar collector with flat plates can easily achieve relatively high water temperature levels of 70 °C in the winter season. In addition, using a solar domestic hot water system as a water heater in Baghdad climatic conditions by substituting electric water heaters is useful for saving power consumption

The aim of the current study is to evaluate the performance of a domestic water heating system for residential areas in Baghdad climatic conditions for substituting electric water heaters with solar-powered water heaters using solar collectors. Many countries, such as Iraq, are sluggish with electric power issues while receiving very high solar insolation. Solar energy is a clean, non-depleting and low-cost source that can be used especially in residential areas, which forms a great percentage of energy consumption by replacing electric water heating with solar water heating to reduce electricity usage. Therefore, six flat plate solar collectors with an absorbing area of 1.92×0.85 m with one 4 mm thick glass cover are utilized for experimental investigation under the Baghdad climatic conditions. The collector was tested under steady-state settings, which assumed that sunlight intensity, ambient temperature, and inlet-outdoor temperature difference in each collector in the system were constant throughout the operation. According to the experimental results, during the test months of November, December, January, and February, the time-weighted experimental daily average collector array efficiency is found in the range of 40 % to 60 %. Furthermore, the greater energy gain and performance of the solar collector array attain a peak value at solar noon. Additionally, a solar collector with flat plates can easily achieve relatively high water temperature levels of 70 °C in the winter season. In addition, using a solar domestic hot water system as a water heater in Baghdad climatic conditions by substituting electric water heaters is useful for saving power consumption