Part Of Blade Research Articles

Efficiency improvement of a CAES low aspect ratio radial inflow turbine by NACA blade profile

Compressed Air Energy Storage (CAES) System is a significant technology for renewable energy utilization. As a power generation device in the system, the blade of radial inflow turbine has a lower aspect ratio and tip leakage loss is larger. A novel blade profile based on NACA standard airfoil is proposed and optimized by orthogonal design coupling Computational Fluid Dynamic (CFD) model. The effect of NACA-based profile parameters on isentropic efficiency is obtained and the tip leakage flow loss mechanism is revealed. The applicability of blade with optimal NACA-based profile is investigated under off-design operation and non-uniformity inlet conditions. Results indicate that the optimal NACA-based profile has larger leading edge inscribed circle radius and smaller thickness at trail part of blade which reduces the tip leakage flow velocity near trailing edge and weakens the mixing of the leakage flow and mainstream. As a result, the efficiency of the radial inflow turbine can be increased by 1.26%, 1.20% and 1.99% when the tip clearance are 2%, 4%, and 8%, respectively. The blade with optimal NACA-based profile also increases the efficiency of the radial inflow turbine at different pressure ratios and inlet attack angles and satisfies the deformation and structure strength requirement.

Tunnel Type Wind Mile Design

This study designs a tunnel type wind mill to increase the capability of wind energy capture. The main design works including the wind collection duct which can rotate along with the wind direction. This makes the wind enter the duct in best condition. After the wind enter the duct, both the direction of the duct is changed to vertical direction which makes the wind direction changes to downward. In the meantime, the diameter of the duct is also changed. The change of the diameter of the duct increases the speed of wind flow. A wind turbine with a nose is used to collect the wind energy. The nose makes the speed of the air flow increase more. In addition to the increasing the speed, the other advantage is to make the air flow flows to the outer part of the turbine blades. It is well known that the outer part of the turbine blade can get more energy than the inner part of the blade. This design can more wind energy than regular wind turbine.

Canonical sound fields in the frequency-domain theory of supersonic leading-edge noise

This paper determines the three-dimensional structure of certain single-frequency canonical sound fields occurring in the theory of blade–vortex interaction when the flow velocity relative to the blade is supersonic. A relative velocity of this magnitude occurs at the outer part of the fan blades in an aeroengine, at which the incoming vorticity has either been ingested from the atmosphere or created in the aeroengine itself. The sound fields analysed are those produced by the leading edge of a flat-plate blade at zero angle of attack on being struck by a gust which is either (i) localized along the span, or (ii) non-localized but discontinuous. The canonical gusts of type (i) have either a delta-function or Gaussian shape, and those of type (ii) are either anti-symmetric or described by a Heaviside function; these gusts give rise to the four basic canonical sound fields. The paper also analyses a fifth sound field, produced by a single-frequency top-hat gust. This sound field has a complex structure involving aspects of both (i) and (ii), but can nevertheless be analysed in terms of the canonical sound fields. The main results of the paper are exact and approximate analytical formulae giving the dependence of the acoustic field on gust-shape and flow parameters, and also a simple formula which is ideal for numerical work. The last of these is used to assess in detail the numerical accuracy of all the approximate formulae, which are of either Fresnel or Keller type. A key result is that Keller-type formulae, representing sound rays produced in accord with the geometrical theory of diffraction, have a very wide range of validity. A companion paper (Chapman & Powles 2019) determines the canonical sound fields in the corresponding time-domain theory.

Selective Laser Melting Enabled Additive Manufacturing of Ti-22Al-25Nb Intermetallic: Excellent Combination of Strength and Ductility, and Unique Microstructural Features Associated

To realize near net-shaping of hard-to-process intermetallics is an often challenging but critical issue to their wider industrial applications. In this work, we report that an intermetallic Ti-22Al-25Nb has been successfully fabricated by selective laser melting (SLM). The as-printed samples show a high room-temperature ultimate tensile strength ~1090 MPa and excellent ductility ~22.7%; both values are higher than most conventionally fabricated Ti-22Al-25Nb intermetallic. We clarify the mechanical performance achieved by detailed microstructure analysis, including dislocation analysis and phase constitution analysis. High-density dislocation networks significantly contribute to the strength and ductility, which are further enhanced by the favorable phase constitution, including the nano-scale O phase precipitates within the disordered β phase and disappearance of the brittle α2 phase in the microstructure. Phase evolution during SLM has also been clarified using in situ heating, high-temperature synchrotron X-ray diffraction and Scheil simulation, particularly regarding the O phase's formation. It is demonstrated that O phase is formed by shearing primary cubic B2 phase along (110)[111] direction into an orthorhombic structure under high residual stress. Furthermore, a demonstrative part of turbine blade has been fabricated to highlight the importance of SLM in fabricating critical structural part like the hard-to-process intermetallics.

Large-scale unsteady flow structures in the leakage flow of a low-speed axial fan with rotating shroud

The leakage flow in low-speed fans provided with rotating shroud has been surveyed by means of two-dimensional LDV and PIV. Measurements have been taken upstream of the rotor and in the gap area at different operating conditions. The flow contains both periodic and non-periodic large-scale flow structures, which are responsible for the noise generation. The former structures have been extracted by means of the ensemble average technique, and, in order to study the latter ones, the non-periodic part of the instantaneous velocity field has been analysed by means of the proper orthogonal decomposition technique.In the present fan, the leakage flow consists in a jet which leaves the gap in the diagonal direction. Depending on rotational speed and blade loading, the jet may form a recirculation bubble anchored to the rotor ring or it may turn radially, forming a large recirculating flow zone.Large-scale, periodic vortical structures leaving the gap are convected by the leakage flow, either wrapping around the recirculation bubble or flowing radially outwards with a spiral pattern. In the former case, such structures, though weakened, likely reach the rotor, while, in the latter case, they have not been found at the rotor entrance. Hence, a different degree of mixing takes place which is consistent with the extension of the blade part where the leakage flow is reingested. This is consistent with the differences in acoustic measurements.The POD technique has shown that, at high loading, large-scale non-periodic vortical structures convect towards the rotor inlet. They are weaker though comparable to the periodic ones released from the gap; at low rotational speed they are stronger than at high rotational speed. Non-periodic flow structures may be present in the flow leaving the gap also, but it has not been possible to identify them clearly. Likely, non-periodic flow structures are originated by the ripping of the periodic ones.A possible explanation for the noise generation in fans with rotating shroud is that the periodic pressure field anchored to the rotor results in the release of periodic flow structures from the gap. Then, such structures may reach the rotor or rip during convection, likely resulting in non-periodic ones which are ingested by the rotor. In both cases, the interaction with the rotor blades likely results in noise generation. The degree of prerotation of the leakage flow is consistent with the frequency shift of the narrowband humps observed in the sound pressure spectra.

On the effect of blade deformations on the aerodynamic performance of wind turbine rotors subjected to yawed inflow

This work is aimed to investigate the effects of elastic blade deformations on the aerodynamics of large wind turbine rotors subjected to yawed inflow. Due to the increasing rotor size and advanced light weight blade designs, significant blade deflections can be observed on a regular basis for modern wind turbines. However, especially for complex flow situations like yawed inflow, the role of blade deformations is still not completely understood. In this paper, numerical simulations are conducted on the DTU 10 MW reference wind turbine to gain a better understanding of the involved phenomena. Results are obtained by two numerical methods of different fidelity. First, by the aero-elastic simulation tool FAST, which is based on the low fidelity Blade Element Momentum Theory (BEM) and makes use of common skewed wake correction models. Secondly, by a high-fidelity framework which couples the open-source Computational Fluid Dynamics (CFD) toolbox OpenFOAM with the in-house geometrically non-linear beam solver BeamFOAM. The evaluation of the results is based on the analysis of azimuthal variations of the sectional forces along the blade span and reveals a generally good agreement between the used numerical approach in terms of force amplitudes and variation phases. However, especially for cases of larger yaw angles, the BEM models clearly over-predict the variation amplitudes of the forces up to 40% in the outer blade part.

A method of designing of torque­-flow pump impeller with curvilinear blade profile

The research is devoted to energy efficiency increasing of a “Turo” type torque-flow pump by improving its impeller. This allows minimizing the total pump installation life cycle cost as a result of reducing the costs of electricity. The application of the real fluid flow physical model in a torque-flow pump allowed developing the energy distribution mathematical model in its flowing part. In the proposed mathematical model, the ratio of component flows was defined. These include the toroidal vortex, the flow coming from the impeller intervane channels directly to the outlet (through-flow), and the flow that does not contact with the blades (flowing stream). As a result, it is found that the maximum possible energy efficiency of the torque-flow pump operating process without taking into account hydraulic losses is η op =0.67. The method of designing the torque-flow pump impeller with a curvilinear blade profile is developed. The method is based on the proposed mathematical model of energy distribution in the torque-flow pump flowing part. The blade inlet angle β 1 and the angle on the calculated impeller radius β r are proposed to be carried out in accordance with the fluid flow in the impeller intervane channels. The radius r<r 2 is chosen for which there is a radial motion of the fluid in the intervane channels of the impeller. The numerical investigation made it possible to estimate the fluid flow structure in the torque-flow pump flowing part. Using the proposed impeller has minimized losses at the inlet and in its intervane channels as a result of coordination of the fluid flow and the impeller skeleton geometry. Increasing the blade part and reducing the vortex part of the operating process allowed increasing the energy efficiency of the torque-flow pump. The proposed geometry of the impeller allows increasing the energy efficiency of existing torque-flow pumps by 4–5 %.

Overall design optimization of dedicated outboard airfoils for horizontal axis wind turbine blades

AbstractDesigning the primary airfoils for the outboard part of wind turbine blades is a complicated problem of balancing structural, aerodynamic, and acoustic requirements. This paper presents an optimization method for the overall performance of outboard wind turbine airfoils. Based on the complex flow characteristics of the rotor blades and the varying requirements along the span of a blade, the design principles of outboard airfoils were investigated. The requirements for improving the structural performance and reducing the aerodynamic noise were combined with the following aerodynamic design considerations: high efficiency, low extreme loads, stability, and a wide operating region. Thus, this paper proposes a new mathematical model for overall airfoil optimization using the airfoil performance evaluation indicators. Then, an integrated optimization design platform is established for outboard airfoils. Through 2 design cases, new airfoils with desirable aerodynamic characteristics and improved overall performance were obtained. Comparisons between the new airfoils and reference airfoils based on numerical predictions indicate that the proposed method with the newly established mathematical model can effectively balance the complex requirements of the airfoil and improve its overall performance. More notably, the design cases also indicate that the established optimization design method can be used to address special designs of outboard airfoils for different blade requirements.

Freeform Machining Features: New Concepts and Classification

During the last decades, many researches and applications have been conducted on machining features modeling and classification. Although several approaches have been used in the domain of Computer-Aided Process Planning (CAPP), the consideration of freeform shapes has not been well explored at present. This paper aims to provide an up-to-date review of machining features and its conformance with STEP-NC (STEP compliant Numerical Control). A new method based on discrete shape representation, differential geometry and graph theory is developed for freeform machining feature characterization and classification. The effectiveness of the proposed method is demonstrated through an example of a blade part.

Investigation of Aeroacoustic Properties of Low-Pressure Axial Fans with Different Blade Stacking

Several blade-stacking strategies exist for low-pressure axial fans with potential benefits with respect to the aeroacoustic sound emission. In this study, the impact of such different blade-stacking strategies (including single-type and combined-skewed fan blades) on the fan characteristic curves, aerodynamic properties, and aeroacoustic properties was investigated. It was found that the fan aerodynamic and acoustic characteristic curves are strongly governed by the type of fan blade skew in the outer part of the fan blade. This was also observed for the flow-field on the suction side and on the pressure side. Sound pressure spectra and beamforming sound maps of the fans were further studied for one representative point in the typical fan operating range. The spectra showed similar tendencies as the fan characteristic curves, with spectra progressions being mainly dependent on the type of fan blade skew in the outer part of the fan blade. The sound maps revealed that, for the most part, sound sources are located in the outer fan region but that source characteristics may still be different for single-type and combined-skewed fans. These findings can be further used for reducing the sound emission of low-pressure axial fans with a focus on the fan blade shape in the outer part of the fan blade.

Verification of a novel innovative blade root design for wind turbines using a hybrid numerical method

Abstract To enhance the performance of horizontal axis wind turbines, it is proposed to place a cylindrical disc in front of the rotor in order to lead the incoming flow from the inner part to the outer part of the rotor blades. This is expected to increase the power output, as the kinetic energy is mainly captured at the outer part of the blades, where the relative wind speed is high. To assess the impact of this novel design idea, a hybrid numerical technique, based on solving the Reynolds-averaged Navier-Stokes equations, is utilized to determine the aerodynamic performance. The in-house developed EllipSys3D code, which is employed as basic numerical solver, is combined with an actuator disc representation of the wind turbine rotor and an immersed boundary technique for representing the upstream cylindrical disc. The impact of the disc on the rotor performance is assessed by systematically changing the size of the circular disc and its axial distance to the rotor. Based on a numerical study of a Megawatt size commercial wind turbine, it is found that up to 1.5% additional energy can be captured by placing a circular disc with a suitable diameter upstream of the rotor plane.

Development of thick airfoils for outboard sections and investigation into their application for large rotors

The use of thick airfoils toward the outboard part of horizontal axis wind turbine blades is a promising concept to reduce the cost of wind energy. In fact, thick airfoils have higher area moments of inertia than those of thin airfoils, normally employed toward the outboard part of the blade. Replacing thin airfoils with thicker ones would therefore allow one to improve the structural properties of the blade, reducing the mass needed to ensure its structural integrity. Conventional thick airfoils, however, are generally characterized by worse aerodynamic performance with respect to those of thin airfoils, which make them less attracting for their use toward the outboard part of the blade. The research reported in this paper deals with the development of an optimization system for the aerodynamic design of thick airfoils, aiming to improve their aerodynamic performance, and therefore making them more suitable for their usage toward the outboard part of the blade. In order to determine the effect of the use of thick airfoils towards outboard sections, a blade design incorporating a newly designed 30% thick airfoil is assessed both statically and dynamically. The results showed that mass reduction can be achieved with the use of ad hoc optimized thick airfoils with limited penalty in power production.

Process Modeling of Composite Materials for Wind-Turbine Rotor Blades: Experiments and Numerical Modeling.

The production of rotor blades for wind turbines is still a predominantly manual process. Process simulation is an adequate way of improving blade quality without a significant increase in production costs. This paper introduces a module for tolerance simulation for rotor-blade production processes. The investigation focuses on the simulation of temperature distribution for one-sided, self-heated tooling and thick laminates. Experimental data from rotor-blade production and down-scaled laboratory tests are presented. Based on influencing factors that are identified, a physical model is created and implemented as a simulation. This provides an opportunity to simulate temperature and cure-degree distribution for two-dimensional cross sections. The aim of this simulation is to support production processes. Hence, it is modelled as an in situ simulation with direct input of temperature data and real-time capability. A monolithic part of the rotor blade, the main girder, is used as an example for presenting the results.

Proteomic Analysis of Rice Seedlings Under Cold Stress.

Low temperature can greatly restrict the growth and development of rice. The rice seedlings show growth retardation, lamina wrap, and part of blade even died under the condition of low temperature. In order to get more information about cold stress responses in rice, two dimensional electrophoresis and bioinformatics analysis of mass spectrometry were used to preliminary survey the cold tolerance of cold sensitive line 9311 and cold resistance variety Fujisaka 5 under cold stress. Two dimensional electrophoresis maps of 9311 and Fujisaka 5 were established under cold treatment. With analysis of bioinformation, the proteins were found involve in many aspects of rice development. The largest category of proteins is functioning on metabolism. By comparing the proteins from the two varieties, it can be found that most proteins from 9311 were down-regulated and were up-regulated in Fujisaka 5. The results showed that the membrane composition and structure were damaged, metabolism changed dramatically and rice defense system was activated under the cold stimulation. Fifty-nine proteins related to the resistance of cold stress were identified in our study, and we have investigated and classified all of their biological functions. The importance of our study are providing some conduct for the research of rice resistant to cold stress, supporting auxiliary technique for rice varieties and widening the search field of cold tolerance in plants.

Finite Element Analysis for the Web Offset of Wind Turbine Blade

The web is an important part of wind turbine blade, which improves bending properties. Much of blade process is handmade, so web offset of wind turbine blade is one of common quality defects. In this paper, a 3D parametric finite element model of a blade for 2MW turbine was established by ANSYS. Stress distributions in different web offset values were studied. There were three kinds of web offset. The systematic study of web offset was done by orthogonal experiment. The most important factor of stress distributions was found. The analysis results have certain instructive significance to design and manufacture of wind turbine blade.

Fatigue assessment of a notched member under combined LCF and HCF loading

Steam turbine last stage blades can experience a wide range of load spectra during their lifetime, which involves both Low Cycle Fatigue (LCF) and High Cycle Fatigue (HCF) phenomena.In the paper a numerical model is proposed for considering this specific load spectrum in the fatigue life assessment of turbine blade components made of high strength precipitation-hardening steels.The method is based on cyclic isothermal stress and strain controlled fatigue test results of notched and un-notch specimen up to the HCF-regime. Moreover, stress controlled tests on notched specimens with different stress ratios were performed in order to evaluate the influence of mean stress and to derive a local Haigh diagram. The Highly Stressed Volume (HSV) has been used to transfer characteristic fatigue properties from specimens to a critical area (notched part) of a turbine blade. Furthermore, the real operating conditions of the component were used to allow the application of Palmgren-Miner damage rule.An ad-hoc MATLAB® software has been developed for the post-process of Finite Element Analysis (FEA) results, in particular for the automatic calculation of the HSV on the critical areas of the component. The proposed fatigue model has been finally applied on a real case study (blade dovetail) using appropriate safety margins for reliable design assessment.

수원 입북동 출토 철제환두도의 제철과 제작기술 연구

본 연구는 수원 입북동 출토 철제환두도의 비금속개재물을 SEM-EDS로 분석하여 제철조업 온도를 추정하고 산화물을 <TEX>$SiO_2$</TEX>와 비교하여 조재제의 인위적 장입 여부를 판단하였으며 금속학적인 조직조사를 통하여 철제 환두도의 제작 시 열처리 기술을 연구하였다. 철제환두도의 시편들에서 wustite가 대부분 관찰되는 것으로 보아 고체저온환원법으로 제련한 철 소재를 가열-단조-성형 가공하여 제작된 것으로 판단된다. 또한 부분적으로 <TEX>$P_2O_5$</TEX>가 있는 것으로 보아 배소되지 않은 자연광석으로 직접 제련하였던 것으로 추정된다. <TEX>$CaO/SiO_2$</TEX>와 <TEX>$TiO_2/SiO_2$</TEX> 등의 비로 보아 제철 원료는 철광석으로 판단되며, 석회질의 조재제도 인위적으로 장입하지는 않은 것으로 판단된다. 선단 쪽 인부의 조직은 순철인데 관부 쪽 인부는 탄소량도 높고 martensite 조직과 pearlite colony가 생성되어 있는 것으로 보아 침탄 후 담금질을 하였으며, 배부 및 병부와 환두부는 의도하지 않은 침탄이 된 것으로 판단된다. 이러한 철제환두도 시편들의 조직 양상들을 종합해본 결과 인위적인 부분적인 열처리 기법을 적용하여 제작한 것을 알 수 있었다. 본 연구에서는 한 유물에서나타나는 비금속개재물의 성분분석을 통해 얻은 산화물 데이터를 <TEX>$SiO_2$</TEX>로 나눈 비로 비교하는 해석하는 방법을 활용하여 좀 더 과학적인 근거를 제시하려고 노력하였다. 이러한 방법으로 기존의 분석 연구된 결과들에 의한 주장들을 재해석함으로 해서 다른 결과들을 얻을 수 있을 거라 사료된다. This study analyzed nonmetallic inclusions in iron swords with a ring pommel excavated in the Ipbuk-dong, Suwon. Scanning electron microscopy with energy dispersive spectroscopy(SEM-EDS) was used to estimate the iron-making temperature, and we compared the oxide with <TEX>$SiO_2$</TEX> to investigate the heat-treatment technology in the production of iron swords with a ring pommel by investigating the artificial insertion of a slag former and the metallurgical structure. From the wustite observed in most of the specimens, it is judged that these swords were produced by heating and forging iron smelted at a low temperature using the solid reduction method. In addition, judging from the partial presence of <TEX>$P_2O_5$</TEX>, it is assumed that they were smelted directly with natural ore, not calcined. From the ratios of <TEX>$CaO/SiO_2$</TEX> and <TEX>$TiO_2/SiO_2$</TEX>, it is judged that the raw material for iron-making was iron ore and that a calcareous slag former was not artificially inserted. The structure of the blade part on the front end was pure iron. From the high carbon content of the blade part on the ring pommel and the formation of a martensitic structure and pearlite colony, it is judged that they were tempered after carburizing and that the back, handle part, and ring pommel were unintentionally carburized. Judging from the structure of these specimens, it was noted that they were produced by applying artificial partial heat-treatment technology. This study attempted to present a more scientific analysis by using the method of interpretation through component analysis of nonmetallic inclusions appearing in one relic by the ratio of the oxide divided by <TEX>$SiO_2$</TEX>. It is judged that reinterpreting the arguments by the results of the existing analysis and research in this way can obtain different interpretations.

Numerical research on effect of transition on aerodynamic performance of wind turbine blade with vortex generators

In the inner part of a large wind turbine blade, a thick airfoil is commonly used to guarantee structural integrity and assists the blade to run more easily at high angles of attack in variable winds; its local Reynolds number is less than 3.0 × 106. Under these conditions, flow separation and transitions easily occur and exert great impact on blade performance. Vortex generators (VGs) are effective devices used to control flow separation and alter stalling conditions, and hence have been employed in the inner part of the blade in some wind turbines. To clearly understand the aerodynamic performance of a blade with VGs, a blade section employing the thick DU91-W2-250 airfoil and five pairs of VGs is modeled using the transition model. The results for both the coefficient of lift and drag–lift ratio predicted by the transition model are compared with those obtained from the k-ω shear stress transport model and experiment. The comparison demonstrates that the transition model has much higher accuracy. The effects of transition on the distributions of flow stream, shear stress, and vortices from the VGs are investigated and more useful rules are obtained through a comparison between the results of the transition model and the turbulence model at four angles of attack: 5°, 12°, 16°, and 20°.

Numerical simulation on vacuum solution heat treatment and gas quenching process of a low rhenium-containing Ni-based single crystal turbine blade

Numerical heat-transfer and turbulent flow model for an industrial high-pressure gas quenching vacuum furnace was established to simulate the heating, holding and gas fan quenching of a low rhenium-bearing Ni-based single crystal turbine blade. The mesh of simplified furnace model was built using finite volume method and the boundary conditions were set up according to the practical process. Simulation results show that the turbine blade geometry and the mutual shielding among blades have significant influence on the uniformity of the temperature distribution. The temperature distribution at sharp corner, thin wall and corner part is higher than that at thick wall part of blade during heating, and the isotherms show a toroidal line to the center of thick wall. The temperature of sheltered units is lower than that of the remaining part of blade. When there is no shelteration among multiple blades, the temperature distribution for all blades is almost identical. The fluid velocity field, temperature field and cooling curves of the single and multiple turbine blades during gas fan quenching were also simulated. Modeling results indicate that the loading tray, free outlet and the location of turbine blades have important influences on the flow field. The high-speed gas flows out from the nozzle is divided by loading tray, and the free outlet enhanced the two vortex flow at the end of the furnace door. The closer the blade is to the exhaust outlet and the nozzle, the greater the flow velocity is and the more adequate the flow is. The blade geometry has an effect on the cooling for single blade and multiple blades during gas fan quenching, and the effects in double layers differs from that in single layer. For single blade, the cooing rate at thin-walled part is lower than that at thick-walled part, the cooling rate at sharp corner is greater than that at tenon and blade platform, and the temperature at regions close to the internal position is decreased more slowly than that close to the surface. For multiple blades in single layer, the temperature at sharp corner or thin wall in the blade that close to the nozzles is much lower, and the temperature distribution of blades is almost parallel. The cooling rate inside the air current channel is lower than that of at the position near blade platform and tenon, and the effect of blade location to the nozzles on the temperature field inside the blade is lower than that on the blade surface. For multiple blades in double layers, the flow velocity is low, and the flow is not uniform for blades in the second-layer due to the shielding of blades in the first-layer. the cooling rate of blades in the second-layer is lower than that in the first-layer. The cooling rate of blade close to the nozzles in the first-layer is the higher than that of blade away from the nozzles in the second-layer, and the temperature distribution on blades in the same layer is almost parallel. The cooling rate in thin wall position of blade away from the nozzles is larger than that in tenon of the blade closer to the nozzles in the same layer. The cooling rate for blades in the second- layer is much lower both in thin wall and tenon for blades away from the nozzles.

Severing of skull cap: A rare trauma attributed to transportation of bulldozer.

Bulldozer fatalities are usually due to accidental crushing of the body at the workplace. However, severance of the skull cap simulating a chopping injury to head is rare in the literature. Medico-legal investigation may be posed with different challenges when carrying out an autopsy of a victim with this devastating head injury. The police will seek an opinion about the type of weapon responsible for the injuries, the nature of injuries produced and manner of death. In the present case, the victim was hit at dusk by a protruding part of the bulldozer blade as he crossed in front of a bulldozer that was approaching his tractor from the opposite side of the road. His skull cap was severed and he died instantly. This report considers the circumstances of his death, its mechanisms and strategies for preventing such deaths.